blk_cleanup_queue() may be called before elevator is set up on a queue which triggers the following oops. BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff8125a69c>] elv_drain_elevator+0x1c/0x70 ... Pid: 830, comm: kworker/0:2 Not tainted 3.1.0-next-20111025_64+ #1590 Bochs Bochs RIP: 0010:[<ffffffff8125a69c>] [<ffffffff8125a69c>] elv_drain_elevator+0x1c/0x70 ... Call Trace: [<ffffffff8125da92>] blk_drain_queue+0x42/0x70 [<ffffffff8125db90>] blk_cleanup_queue+0xd0/0x1c0 [<ffffffff81469640>] md_free+0x50/0x70 [<ffffffff8126f43b>] kobject_release+0x8b/0x1d0 [<ffffffff81270d56>] kref_put+0x36/0xa0 [<ffffffff8126f2b7>] kobject_put+0x27/0x60 [<ffffffff814693af>] mddev_delayed_delete+0x2f/0x40 [<ffffffff81083450>] process_one_work+0x100/0x3b0 [<ffffffff8108527f>] worker_thread+0x15f/0x3a0 [<ffffffff81089937>] kthread+0x87/0x90 [<ffffffff81621834>] kernel_thread_helper+0x4/0x10 Fix it by making blk_cleanup_queue() check whether q->elevator is set up before invoking blk_drain_queue. Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Reported-and-tested-by: Jiri Slaby <jslaby@xxxxxxx> --- block/blk-core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index f658711..f43c8a5 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -407,8 +407,13 @@ void blk_cleanup_queue(struct request_queue *q) spin_unlock_irq(lock); mutex_unlock(&q->sysfs_lock); - /* drain all requests queued before DEAD marking */ - blk_drain_queue(q, true); + /* + * Drain all requests queued before DEAD marking. The caller might + * be trying to tear down @q before its elevator is initialized, in + * which case we don't want to call into draining. + */ + if (q->elevator) + blk_drain_queue(q, true); /* @q won't process any more request, flush async actions */ del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer); -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
